1. Field of the Invention
The present invention relates to a brightness enhancement film having a light-guiding structure for use in a liquid crystal display. Particularly, the present invention relates to the brightness enhancement film including a light-guiding layer and a light-refracting microstructure layer at either side thereof. More particularly, the present invention relates to the brightness enhancement film using the light-refracting microstructure to generate refracted light, and the light-guiding layer to guide the refracted light for providing homogeneous light.
2. Description of the Related Art
Referring initially to FIG. 1, U.S. Pat. No. 5,626,800, entitled “Prevention of Groove Tip Deformation in Brightness Enhancement Film,” discloses a brightness enhancement film including a substrate (i.e. base) and a plurality of prism units provided thereon. The prism units are arranged and juxtaposed on a top surface (i.e. light emission surface) of the substrate in order. Each of the prism units located on the light emission surface consists of a first inclined surface and a second inclined surface connected thereto, and serves to refract light, which had penetrated through the substrate, in use for enhancing brightness of light.
The substrate of the brightness enhancement film has a bottom surface (i.e. light incident surface) which is an ordinary flat surface and opposite to the top surface. In use, light projected from a light source enters the flat surface of the bottom surface and then passes through the substrate. Subsequently, the light can further pass through the top surface of the substrate, and the prism units of the substrate eventually refract the light such that the refracted light can be generated from the light emission surface of the substrate.
However, the substrate of the brightness enhancement film permits directly emitting the refracted light from the light emission surface of the substrate without passing it through any guiding means. The light emission surface of the substrate cannot generate homogeneous refracted light due to the lack of any guiding means disposed on the light emission surface. In other words, the refracted light can appear a degree of homogeneous characteristic if the light emission surface of the substrate is provided with an additional light-guiding layer to solve the above problem. Another problem with the manufacture of such an additional light-guiding layer raises difficulty in reducing the entire thickness of the substrate of the brightness enhancement film. Hence, there is a need for improving the conventional brightness enhancement film in both enhancing homogeneous light and reducing a thickness of the substrate.
Another problem with the manufacture of the substrate of the conventional brightness enhancement film generally forms a bottom surface which is an ordinary flat surface without forming any structure and opposite to the top surface on which to provide the microstructure of the prism units. However, the top surface and the bottom surface disposed on the substrate of the brightness enhancement film are unmatched in structure which may cause a specific degree of warpage of the brightness enhancement film in nature. Furthermore, the brightness enhancement films are piled upon each other on a conveyer if the products are finally made. This practice unavoidably causes warpage and abrasion between the surfaces of the separate brightness enhancement films, and disadvantageously affects quality and quantity of output of the brightness enhancement films.
U.S. Pat. No. 6,280,063, entitled “Brightness Enhancement Article,” also discloses another brightness enhancement film including a substrate, a prism unit layer and a light-diffusing surface. The prism unit layer and the light-diffusing surface serve as a top surface (i.e. light emission surface) and a bottom surface (i.e. light incident surface) of the substrate. This permits light to penetrate through the substrate from the light-diffusing surface to the prism unit layer where light is emitted. Typically, the light-diffusing surface contains several light-diffusing particles which naturally diffuse light. Correspondingly, the prism unit layer is used to refract light penetrating the brightness enhancement film.
Similarly, the substrate of the brightness enhancement film permits directly emitting the refracted light from the light emission surface of the substrate without passing it through any guiding means. Also, the light emission surface of the substrate cannot generate homogeneous refracted light if the light emission surface of the substrate is provided with no light-guiding layer to solve this problem. Inevitably, another problem with the manufacture of such an additional light-guiding layer raises difficulty in reducing the entire thickness of the substrate of the brightness enhancement film. There is an unavoidable need for improving such a brightness enhancement film in both enhancing homogeneous light and reducing a thickness of the substrate.
Even though the brightness enhancement film has the light-diffusing surface at its bottom side, the light-diffusing surface is still inadequate to prevent warpage of the brightness enhancement film in nature. Furthermore, the light-diffusing particles of the brightness enhancement film protrude like raised particles on the light-diffusing surface and, thus, scrape the surface of another brightness enhancement film while piling upon each other. Also, this practice unavoidably causes warpage and abrasion of the surfaces of the brightness enhancement films and disadvantageously affects quality and quantity of output of the brightness enhancement films.
There are numerous other patent publications, for instance, U.S. Pat. No. 6,354,709, U.S. Pat. No. 6,707,611, U.S. Pat. No. 6,669,350, and U.S. Pat. No. 6,339,458, etc., that describe a brightness enhancement film but fail to provide light-guiding means on the light emission surface for enhancing brightness.
The present invention intends to provide a brightness enhancement film having a plurality of light-refracting microstructures and a light-guiding layer, wherein the light-refracting microstructures are arranged on a light incident surface while the light-guiding layer is arranged on a light emission surface. The light-refracting microstructure can refract light, and subsequently, the light-guiding layer can guide the refracted light for providing homogeneous light in such a way as to mitigate and overcome the above problem.
In addition, the present invention also intends to provide the brightness enhancement film having a reinforcing layer at one side thereof. The reinforcing layer provides a specific degree of hardness, thereby preventing the brightness enhancement film from occurrence of warpage and abrasion by another in such a way as to mitigate and overcome the above problem.